The objective of this research proposal is to obtain a better understanding of the neuronal mechanisms involved in visual search. Investigating these mechanisms will also provide information of the interaction between working memory with visual attention systems. An understanding of these mechanisms in the healthy primate is required in order to understand their contribution to the residual visual abilities in man following brain damage. Recent observations in the sponsor's laboratory have shown that the selection of objects in visual search are coded by neurons in inferotemporal (IT) cortex. However, it is not known whether this selection mechanism is confined to IT cortex or is a more general property of extrastriate visual areas. The selection of objects based on simple features such as color or orientation may be expected to involve prestriate areas concerned with such fares. The principle aim of this study is to test the hypothesis that the selection of objects in visual search is not unique to IT cortex and occurs at earlier levels of processing, particularly prestriate area V4. This will be achieved by recording from single neurons in earlier prestriate areas (e.g. area V4) whilst a monkey is performing a visual search task.